Electronic scales can be classified primarily into a load cell type using a strain gauge, a tuning fork vibration type using a tuning fork vibrator and an electromagnetic balancing type using an electromagnet and an electromagnetic coil.
The load cell type makes weight measurements based on the amount of transformation of the strain gauge by a load of an object to be weighed. As disclosed in the following Patent Document 1, the timing fork vibration type makes weight measurements using the fact that vibration frequency of the tuning fork varies in proportion to the load to be applied between both ends of the tuning fork. On the other hand, the electromagnet balancing type breaks the balanced condition of a mechanical balance mechanism and recovers the balanced condition by flowing electric current through the electromagnetic coil, thereby determining the weight of the load based on the amplitude of the electric current.
As far as precision of these scales is concerned, the tuning fork vibrator type and the electromagnetic balancing type are higher than the load cell type. On the other hand, in the manufacturing cost of these scales, the electromagnetic balancing type is the highest because of its complex construction and the load cell type is the lowest because of its simple construction.
Currently, most of platform scales having a weighing range (measurement range) up to 300 kg are the load cell type.